1. Field of the Invention
The present invention relates to an electron beam exposure apparatus and, more particularly, to an electron beam exposure apparatus for drawing a pattern on a wafer or drawing a pattern on a mask or reticle using a plurality of electron beams, and its control method.
2. Description of the Related Art
An electron beam exposure apparatus includes a point beam type apparatus which uses a beam shaped in a spot pattern, a variable rectangular beam type apparatus which uses a beam shaped to have a rectangular section with a variable size, a stencil mask type apparatus which shapes a beam into a desired sectional shape using a stencil, and the like.
The point beam type electron beam exposure apparatus is used for only research purposes due to its low throughput. The variable rectangular beam type electron beam exposure apparatus has a throughput higher by one or two orders of magnitude than that of the point beam type, but suffers problems in terms of throughput when highly integrated patterns having a line width as small as about 0.1 xcexcm are to be formed by exposure. On the other hand, the stencil mask type electron beam exposure apparatus uses a stencil mask formed with a plurality of repetitive pattern through holes in a portion corresponding to a variable rectangular aperture. Hence, the stencil mask type electron beam exposure apparatus is effective for exposure of repetitive patterns. However, when a semiconductor circuit requires a large number of transfer patterns that cannot be formed on a single stencil mask, a plurality of stencil masks must be prepared in advance, and must be used one by one, resulting in a long mask exchange time and a considerable throughput drop.
As an apparatus that can solve the above problems, a multi-electron beam type exposure apparatus is known. In this apparatus, a plurality of electron beams are irradiated on the sample surface along the course of design coordinate positions, and are deflected along that course of design coordinate positions to scan the sample surface. In addition, the plurality of electron beams are individually ON/OFF-controlled in correspondence with the pattern to be drawn, thereby drawing the pattern. Since the multi-electron beam type exposure apparatus can draw an arbitrary pattern, it can improve the throughput.
FIG. 15A schematically shows the multi-electron beam type exposure apparatus. Reference numerals 501a, 501b, and 501c denote electron guns that can individually ON/OFF-control electron beams. Reference numeral 502 denotes a reduction electron optical system for projecting a plurality of electron beams emitted by the electron guns 501a, 501b, and 501c onto a wafer 503 in a reduced scale; and 504, a deflector for deflecting the plurality of electron beams to be projected onto the wafer 503 in the reduced scale.
The plurality of electron beams coming from the electron guns 501a, 501b, and 501c are deflected by an identical amount by the deflector 504. With this deflection, the respective electron beams are deflected while sequentially settling their positions on the wafer in accordance with a matrix having a matrix spacing defined by the minimum deflection width of the deflector 504 with reference to their beam reference positions. The individual electron beams form exposure patterns on different exposure regions by exposure.
FIGS. 15B to 15D show the state wherein the electron beams coming from the electron guns 501a, 501b, and 501c expose the corresponding exposure regions to form exposure patterns in accordance with an identical matrix. The respective electron beams move while settling their positions on the matrix at the same time like (1, 1), (1, 2), . . . , (1, 16), (2, 1), (2, 2), . . . , (2, 16), (3, 1), . . . , and expose the corresponding regions to form patterns (P1, P2, P3) by turning on the beams at the positions of the exposure patterns (P1, P2, P3).
In the multi-electron beam type exposure apparatus, since the respective beams simultaneously form different patterns, the size of each electron beam and the minimum deflection width of the deflector 504 corresponding to that size are set in correspondence with the minimum line width of the exposure patterns. As the minimum line width becomes smaller, the number of times of exposure while settling the electron beam positions increases, resulting in a considerable throughput drop.
The exposure patterns do not always equally include patterns with a minimum line width. However, conventionally, even in a region defined by a pattern having a line width larger than the minimum line width, exposure is done using the electron beam size and the minimum deflection width corresponding to that size, determined based on the minimum line width in all the patterns. For this reason, the throughput drops as the minimum line width of the pattern shrinks.
It is an object of the present invention to achieve high throughput by dynamically changing the dot pattern size to be formed on the object to be exposed upon forming a single pattern by exposure.
An electron beam exposure apparatus according to one aspect of the present invention is an electron beam exposure apparatus for drawing a pattern on an object to be exposed using a plurality of electron beams, comprising an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed and an adjustment unit for dynamically adjusting sizes of dot patterns formed on the object to be exposed upon projection of the intermediate images in correspondence with fields to be exposed of the pattern to be drawn by exposure on the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts the sizes of the intermediate images to be projected onto the object to be exposed, thereby dynamically adjusting the sizes of the dot patterns to be formed on the object to be exposed.
The electron beam exposure apparatus further comprises an illumination electron optical system which is inserted between the electron source and the plurality of elementary electron optical systems, and is adapted to convert the electrons emitted by the electron source into substantially collimated electron beams, and to irradiate the electron beams onto the plurality of elementary electron optical systems, and wherein the adjustment unit adjusts the focal length of the illumination electron optical system to adjust the sizes of the intermediate images to be projected onto the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit adjusts the focal length of the illumination optical system while fixing a focal point position of the illumination electron optical system on the electron source side.
In the electron beam exposure apparatus, the illumination electron optical system comprises a plurality of electron lenses disposed in an optical axis direction, and the adjustment unit adjusts the focal length of the illumination electron optical system while fixing the focal point position of the illumination electron optical system on the electron source side, by changing focal lengths of at least two of the plurality of electron lenses.
The electron beam exposure apparatus further comprises an axis correction unit for correcting position deviations of the intermediate images to be projected onto the object to be exposed produced when the adjustment unit adjusts the focal length of the illumination electron optical system.
In the electron beam exposure apparatus, the axis correction unit corrects the position deviations of the intermediate images of the electron source to be projected onto the object to be exposed by correcting positions of the plurality of intermediate images formed immediately below the plurality of elementary electron optical systems.
The electron beam exposure apparatus further comprises a scanning unit for scanning the intermediate images to be projected onto the object to be exposed, and wherein the adjustment unit dynamically adjusts a minimum scanning width of the scanning unit in correspondence with the sizes of the dot patterns to be formed on the object to be exposed.
In the electron beam exposure apparatus, the scanning unit comprises a deflector for deflecting electron beams to be irradiated from the plurality of elementary electron optical systems onto the object to be exposed, and the adjustment unit dynamically adjusts a minimum deflection width of the deflector in correspondence with the sizes of the dot patterns to be formed on the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts a scanning cycle of the scanning unit in correspondence with the minimum scanning width of the scanning unit.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts a deflection cycle of the scanning unit in correspondence with the minimum deflection width of the deflector.
In the electron beam exposure apparatus, the plurality of elementary electron optical systems have a function of correcting any aberrations produced upon projecting the plurality of intermediate images formed by the plurality of elementary electron optical systems onto the object to be exposed via the projection electron optical system.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts the sizes of the dot patterns to be formed on the object to be exposed by projecting the intermediate images in accordance with a unit exposure field to be exposed of the entire field of the pattern to be drawn by exposure on the object to be exposed, the entire field being made up of a set of a plurality of unit exposure fields.
In the electron beam exposure apparatus, the adjustment unit adjusts the sizes of the dot patterns to be formed on the object to be exposed by projecting the intermediate images in units of unit exposure fields on the basis of a feature of an exposure pattern in the corresponding unit exposure field.
In the electron beam exposure apparatus, the adjustment unit adjusts the sizes of the dot patterns to be formed on the object to be exposed by projecting the intermediate images in units of unit exposure fields on the basis of a minimum line width of an exposure pattern in the corresponding unit exposure field.
According to another aspect of the present invention, an electron beam exposure apparatus for drawing a pattern on an object to be exposed using a plurality of electron beams, comprises an electron source for emitting electrons, a projection electron optical system for projecting an image of the electron source onto the object to be exposed, and an adjustment unit for dynamically adjusting a size of a dot pattern formed on the object to be exposed upon projection of the image of the electron source in correspondence with fields to be exposed of the pattern to be drawn by exposure on the object to be exposed.
According to still another aspect of the present invention, a method of controlling an electron beam exposure apparatus, which has an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, and a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed, comprises the step of dynamically adjusting sizes of dot patterns formed on the object to be exposed upon projection of the intermediate.images in correspondence with fields to be exposed of a pattern to be drawn by exposure on the object to be exposed.
According to still another aspect of the present invention, a method of controlling an electron beam exposure apparatus, which has an electron source for emitting electrons, and a projection electron optical system for projecting an image of the electron source onto the object to be exposed, comprises the step of dynamically adjusting a size of a dot pattern formed on the object to be exposed upon projection of the image of the electron source in correspondence with fields to be exposed of a pattern to be drawn by exposure on the object to be exposed.
According to still another aspect of the present invention, a method of generating exposure control data used for controlling an electron beam exposure apparatus, which has an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, and a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed, comprises the steps of dividing a pattern to be drawn by exposure on the object to be exposed into a plurality of blocks, detecting features of patterns in the blocks, determining sizes of dot patterns to be formed on the object to be exposed by projecting the intermediate images in units of blocks on the basis of the features of the patterns in the blocks, and generating exposure control data on the basis of the determination result.
It is another object of the present invention to achieve high throughput by dynamically changing the minimum scanning width for scanning an intermediate image on the object to be exposed upon forming a single pattern by exposure.
An electron beam exposure apparatus according to one aspect of the present invention is an electron beam exposure apparatus for drawing a pattern on an object to be exposed using a plurality of electron beams, comprising an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed, a scanning unit for scanning the plurality of intermediate images to be projected onto the object to be exposed, and an adjustment unit for dynamically adjusting a minimum scanning width of the scanning unit in correspondence with fields to be exposed of the pattern to be drawn by exposure on the object to be exposed.
In the electron beam exposure apparatus, the scanning unit comprises a deflector, and the adjustment unit dynamically adjusts a minimum deflection width of the deflector in correspondence with the fields to be exposed of the pattern to be drawn by exposure on the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts the minimum scanning width of the scanning unit in accordance with a unit exposure field to be exposed of the entire field of the pattern to be drawn by exposure on the object to be exposed, the entire field being made up of a set of a plurality of unit exposure fields.
In the electron beam exposure apparatus, the adjustment unit adjusts the minimum scanning width of the scanning unit, to a minimum scanning width determined based on a minimum line width of an exposure pattern in the corresponding unit exposure field, in units of unit exposure fields.
In the electron beam exposure apparatus, the adjustment unit controls the scanning unit to scan electron beams without settling the electron beams in correspondence with a field, where none of the intermediate images are projected, i.e., no electron beams are irradiated onto the object to be exposed, of exposure fields of the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts a scanning cycle of the scanning unit in correspondence with the minimum scanning width of the scanning unit.
In the electron beam exposure apparatus, the adjustment unit adjusts a deflection cycle of the deflector in correspondence with the minimum deflection width of the deflector.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts the sizes of the intermediate images to be projected onto the object to be exposed in correspondence with the minimum scanning width of the scanning unit.
The electron beam exposure apparatus further comprises an illumination electron optical system which is inserted between the electron source and the plurality of elementary electron optical systems, and is adapted to convert the electrons emitted by the electron source into substantially collimated electron beams, and to irradiate the electron beams onto the plurality of elementary electron optical systems, and wherein the adjustment unit dynamically adjusts the sizes of the intermediate images to be projected onto the object to be exposed by adjusting a focal length of the illumination electron optical system.
In the electron beam exposure apparatus, the deflector comprises first and second deflectors, the first deflector scans the intermediate images to be projected onto the object to be exposed within an elementary exposure field so as to expose a subfield made up of a set of elementary exposure fields, and the second deflector switches the subfield to be exposed every time exposure of the subfield is complete.
In the electron beam exposure apparatus, the first deflector comprises an electrostatic type deflector, and the second deflector comprises an electromagnetic type deflector.
According to the another aspect of the present invention, a method of controlling an electron beam exposure apparatus, which has an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed, and a scanning unit for scanning the plurality of intermediate images to be projected onto the object to be exposed, comprises the step of dynamically adjusting a minimum scanning width of the scanning unit in correspondence with fields to be exposed of a pattern to be drawn by exposure on the object to be exposed.
According to still another aspect of the present invention, a method of controlling an electron beam exposure apparatus, which has an electron source for emitting electrons, a projection electron optical system for projecting an image of the electron source onto the object to be exposed, and a scanning unit for scanning the image of the electron source to be projected onto the object to be exposed, comprises the step of dynamically adjusting a minimum scanning width of the scanning unit in correspondence with fields to be exposed of a pattern to be drawn by exposure on the object to be exposed.
According to still another aspect of the present invention, a method of generating exposure control data used for controlling an electron beam exposure apparatus, which has an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed, and a scanning unit for scanning the plurality of intermediate images to be projected onto the object to be exposed, comprises the steps of dividing a pattern to be drawn by exposure on the object to be exposed into a plurality of blocks, detecting features of patterns in the blocks, determining minimum scanning widths of the scanning unit in units of blocks on the basis of the features of the patterns in the blocks, and generating exposure control data on the basis of the determination result.
It is still another object of the present invention to achieve high throughput by dynamically changing the deflection width of an electron beam and the moving velocity of a stage upon forming a single pattern by exposure.
An electron beam exposure apparatus according to one aspect of the present invention is an electron beam exposure apparatus, which has an electron beam source for generating a plurality of electron beams, a projection electron optical system for projecting images formed by the plurality of electron beams onto an object to be exposed, a deflector for deflecting the plurality of electron beams, and a stage for moving the object to be exposed, and which sequentially exposes divided exposure fields obtained by dividing an exposure pattern in a moving direction of the stage while continuously moving the object to be exposed by the stage, comprising a deflection width adjustment unit for dynamically adjusting a minimum deflection width of the deflector in correspondence with the fields to be exposed of the exposure pattern, and a moving velocity adjustment unit for dynamically adjusting moving velocities of the stage in units of divided exposure fields in correspondence with exposure times required for exposing the respective divided exposure fields while deflecting the plurality of electron beams by the deflector.
In the electron beam exposure apparatus, the moving velocity adjustment unit adjusts the moving velocities of the stage in units of divided exposure fields so as to make the stage move by a length of the corresponding divided exposure field in the moving direction of the stage within the exposure time of the divided exposure field.
In the electron beam exposure apparatus, each of the divided exposure fields is made up of at least one unit exposure field formed by a matrix of a plurality of elementary exposure fields each of which is exposed by one electron beam, and the deflection width adjustment unit adjusts the minimum deflection width of the deflector in units of unit exposure fields.
In the electron beam exposure apparatus, each of the divided exposure fields is made up of a matrix of a plurality of unit exposure fields in directions perpendicular to the moving direction of the stage.
In the electron beam exposure apparatus, the deflection width adjustment unit adjusts the minimum deflection width of the deflector in units of unit exposure fields on the basis of a feature of an exposure pattern in the corresponding unit exposure region.
In the electron beam exposure apparatus, the deflection width adjustment unit adjusts the minimum deflection width of the deflector in units of unit exposure fields on the basis of a minimum line width of an exposure pattern in the corresponding unit exposure region.
The electron beam exposure apparatus further comprises an adjustment unit for adjusting sizes of the electron beams on the object to be exposed in correspondence with the minimum deflection width of the deflector.
In the electron beam exposure apparatus, the exposure time for each unit divided exposure field is determined on the basis of the number of times of settlement, a settling wait time, and a settling time of the electron beam in the corresponding divided exposure field.
In the electron beam exposure apparatus, the moving velocity adjustment unit adjusts the moving velocities of the stages in units of divided exposure fields to fall within a range in which a difference between the moving velocity of the stage upon exposing one divided exposure field, and the moving velocity of the stage upon exposing the neighboring divided exposure field of the one divided exposure field becomes not more than a predetermined value.
According to another aspect of the present invention, an electron beam exposure apparatus, which has an electron beam source for generating a plurality of electron beams, a projection electron optical system for projecting images formed by the plurality of electron beams onto an object to be exposed, a deflector for deflecting the plurality of electron beams, and a stage for moving the object to be exposed, and which sequentially exposes frames obtained by dividing an exposure pattern along a moving direction of the stage while continuously moving the object to be exposed by the stage, comprises a deflection width adjustment unit for dynamically adjusting a minimum deflection width of the deflector in correspondence with fields to be exposed of the exposure pattern, and a moving velocity adjustment unit for adjusting moving velocities of the stage in units of frames.
According to still another aspect of the present invention, a method of controlling an electron beam exposure apparatus, which has an electron beam source for generating a plurality of electron beams, a projection electron optical system for projecting images formed by the plurality of electron beams onto an object to be exposed, a deflector for deflecting the plurality of electron beams, and a stage for moving the object to be exposed, and which sequentially exposes divided exposure fields obtained by dividing an exposure pattern in a moving direction of the stage while continuously moving the object to be exposed by the stage, comprises the deflection width adjustment step of dynamically adjusting a minimum deflection width of the deflector in correspondence with the fields to be exposed of the exposure pattern, and the moving velocity adjustment step of dynamically adjusting moving velocities of the stage in units of divided exposure fields in correspondence with exposure times required for exposing the respective divided exposure fields while deflecting the plurality of electron beams by the deflector.
According to still another aspect of the present invention, a method of controlling an electron beam exposure apparatus, which has an electron beam source for generating a plurality of electron beams, a projection electron optical system for projecting images formed by the plurality of electron beams onto an object to be exposed, a deflector for deflecting the plurality of electron beams, and a stage for moving the object to be exposed, and which sequentially exposes frames obtained by dividing an exposure pattern along a moving direction of the stage while continuously moving the object to be exposed by the stage, comprises the deflection width adjustment step of dynamically adjusting a minimum deflection width of the deflector in correspondence with fields to be exposed of the exposure pattern, and the moving velocity adjustment step of adjusting moving velocities of the stage in units of frames.
According to still another aspect of the present invention, a method of generating exposure control data used for controlling an electron beam exposure apparatus, which has an electron beam source for generating a plurality of electron beams, a projection electron optical system for projecting images formed by the plurality of electron beams onto an object to be exposed, a deflector for deflecting the plurality of electron beams, and a stage for moving the object to be exposed, and which sequentially exposes divided exposure fields obtained by dividing an exposure pattern in a moving direction of the stage while continuously moving the object to be exposed by the stage, comprises the steps of dividing the exposure pattern into a plurality of blocks, detecting features of exposure patterns in the blocks, determining minimum deflection widths of the deflector in units of blocks on the basis of the features of the exposure patterns in the blocks, calculating exposure times required for exposing individual divided exposure fields, each of which includes at least one block, while deflecting the plurality of electron beams by the deflector, on the basis of the minimum deflection widths and shapes of the exposure patterns pertaining to the respective blocks, determining moving velocities of the stages in units of divided exposure fields in accordance with the calculated exposure times of the individual divided exposure fields, and generating exposure control data on the basis of the determined minimum deflection widths and moving velocities.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.